Is the frequency and magnitude of flooding in Western Washington increasing?
Certainly the flooding last year was unusually severe. In some basins, for example the Green and Puyallup, two floods occurred each of which exceeded all previous floods in the basins. This is an extremely unusual occurrence. However, in those same basins no significant floods occurred in the years of 1991 through March 1995. Some statistical evidence indicates that the magnitude of floods is increasing. However, because of the natural variability of rainfall and runoff, it is very difficult to prove conclusively that an increase has occurred.
